Await vs Task.Result in an Async Method [duplicate

问题:

This question already has an answer here:

• What is the difference between await Task<T> and Task<T>.Result? 2 answers

What's the difference between doing the following:

async Task<T> method(){
    var r = await dynamodb.GetItemAsync(...)
    return r.Item;
}

vs

async Task<T> method(){
    var task = dynamodb.GetItemAsync(...)
    return task.Result.Item;
}

In my case, for some reason, only the second works. The first one never seems to end.

回答1:

await asynchronously unwraps the result of your task, whereas just using Result would block until the task had completed.

See this explanantion from Jon Skeet.

回答2:

task.Result is accessing the property's get accessor blocks the calling thread until the asynchronous operation is complete; it is equivalent to calling the Wait method. Once the result of an operation is available, it is stored and is returned immediately on subsequent calls to the Result property. Note that, if an exception occurred during the operation of the task, or if the task has been cancelled, the Result property does not return a value. Instead, attempting to access the property value throws an AggregateException exception. The only difference is that the await will not block. Instead, it will asynchronously wait for the Task to complete and then resume